The Oceans

This is the planet we live on, and as you know it is mostly blue. The blue is water, which covers about 70 per cent of the earth’s surface. Most of this water is connected. But we divide it into five large oceans, and several smaller, adjacent seas. Here, south of India, is the Indian Ocean.

Here, at the southern tip of Africa, it meets the Atlantic Ocean. The Atlantic is the large ocean between Europe and Africa, on its eastern side, and the Americas on its western side. And here, west of the American continents, is the Pacific Ocean: the world’s biggest ocean. It covers about one third of the world’s surface. In many languages it is called ‘peaceful’.

But it’s not very peaceful at all, and neither are any of the other oceans. Across all the world’s oceans, large waves roll, becoming as high as ships when it’s windy, or when they break near the shore. Furthest north lies the Northern Ocean and furthest south, around the continent of Antarctica: the Southern Ocean. These are the planet’s five oceans. The adjacent seas are much more numerous, and there are two different types.

Here is an example of one of the types of sea: a large area of water, bounded by Central America, South America, and a line of islands. This is the Carribean Sea. It is a marginal sea. And here is an example of the second type of sea. The waters of the Red Sea extend far between two continents, and the only connection to the other oceans is through a small strait at the Red Sea’s mouth.

This type of sea is called a mediterranean sea. There are more examples of mediterranean seas, for instance: the Baltic Sea, and the large area of water between Africa and Europe, which is simply called: The Mediterranean Sea. Seawater is salty. This is because water running over land dissolves salt from the rock and soil, and carries this salt to the sea. When the sun shines on the ocean’s water, making it evaporate, the salt remains.

Therefore, about 3,5 percent of the world’s seawater is salty. That’s why humans can’t drink seawater. The sea is swarming with life in many places, and it was in the sea that life on earth arose about 3,7 billion years ago. Most species can be found close to land, along the coasts. Here, in shallow waters, there is light from the sun, and the water temperature is relatively warm.

Most of the world’s fishing takes place near the coast. Further from the coasts, the sea quickly becomes deep: 11 kilometres in the deepest place. The temperature deep down is only just above zero degrees, and there is not one single ray of sunshine. Everything is pitch black. We know that there is life which is adapted to all different ocean environments, but we do not know a lot about the life forms living at great depths.

However, we do know that they live in an extreme environment, in cold water, with no light, and under extremely high pressure. And we know that many of these life forms look very different from what we are used to.